Gyroslabilized optical radiation deflection device providing a stabilized radiation sensitivity lobe

ABSTRACT

A gyro stabilized optical radiation deflection device which provides a radiation sensitivity lobe which is stabilized against angular motions of the envelope in which the radiation is received or transmitted. Such device consists of a ball-shaped gyro rotor rotating about a spin axis and which is seated in a spherical recess in a support which is fixedly connected to the envelope. The central portions of the rotor and recess, through which the radiation is transmitted, are prisms which are transparent to the radiation. Such prisms together form an adjustable diffraction prism which serves as an optical wedge for directing the radiation in a directive sensitivity lobe, such direction being determined by the angle between a planar wall of the rotor prism and a planar wall of the recess prism. Such prisms are of materials having refractive indices such that an angular change of the spin axis of the gyro rotor will cause a corresponding angular change of the radiation lobe, whereby such lobe will remain parallel with the spin axis and so be independent of angular motions of the envelopes.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a gyrostabilized optical deflection device foruse for in the transmission path from/to a transmitter and/or receiverof radiant energy, preferably electromagnetic radiation, to providetransmission and/or reception of the said energy in a directed radiationsensitivity lobe, which device is mounted within an envelope whichduring operation of the device may be subjected to motions relative tofixed spatial reference directions. Such device comprises a movabledeflection body having a spherical outer contour and which is seated ina spherical recess in a housing fixedly connected to the envelope, sothat it is free to move in three rotational degrees of freedom in suchrecess, means being provided for imparting to the said body a rapid spinrotation about a spin axis which substantially coincides with thedirection of the transmitted or received radiation.

2. Description of the Related Art

Such a device used in a target seeker for projectiles is described inSwedish Pat. No. SE 8502509-6. The movable deflection body therein has areflecting plane surface or mirror adapted to reflect outgoing orincoming electromagnetic energy from/to a transmitter and/or receiver.In order to be able to direct the radiation sensitivity lobe of suchreflection in any desired direction, the said body is adapted tocooperate with a two-axis magnetic torque generator which can transfertorques to the body about two mutually perpendicular axes relative tothe spin axis. By its rotation about the spin axis the said deflectionbody at the same time serves as a gyrostabilized platform. Such a gyrostabilized platform used as deflection device for outgoing or incomingradiation can be utilized in many applications. One application is thatmentioned in the said patent, namely as a gyrostabilized platform intarget seekers for projectiles. Another application is anti-aircraftsights mounted on guns and also other types of sights. In common tothese applications is that it is a desired that outgoing and/or incomingradiation shall remain in a fixed direction despite small angularmovements of the envelope in which the device is mounted. In manyapplications it is furthermore a requirement that it shall be possibleto adjust the radiation sensitivity lobe to any desired direction bycontrolled movement of the platform relative to its own space reference.

SUMMARY OF THE INVENTION

The object of the invention is to solve these problems by means of adeflection device which is mechanically more simple and less bulky thanthat described in the Swedish Pat. No. SE 8502509-6.

According to the invention this is achieved by means of a device of thekind as described in the opening paragraph, characterized in, that thedeflection body rotating about the spin axis, is a gyro rotor which incombination with the housing seat which supports the rotor constitutesan adjustable diffraction prism for the radiation. At least a centralpart of the gyro rotor and the said seat, where the radiation passes, isa prism transparent to the radiation, the seat having a fixed prism wallserving as an input/output surface for the radiation and the gyro rotorhaving an adjustable prism wall also serving as an output/input surface.The refractive index of the materials said parts of the of which thesaid parts of the rotor and seat prisms are made is selected so that anangular change in direction of the spin axis of the gyro rotor resultsin a corresponding angular change in direction of the radiationsensitivity lobe for the outgoing and/or incoming radiation.

By its free support in the spherical recess the gyro rotor will serve asa so called two-axis gyroscope, in which besides its spin rotation therotor is free to make angular motions about two mutually perpendicularaxes relative to the spin axis perpendicular axes. In such a two-axisgyroscope the rotor tends to maintain its angular position in a fixedspatial coordinate system independently of small angular motions of theenvelope supporting the rotor. If in accordance with the invention therotor is used as a diffraction prism in a device for deflecting aradiation beam, and and since when the envelope makes small angularmotions relative to the space fixed rotor the outgoing or incoming beamwill make exactly the same angular motion relative to the envelope asthat between envelope and rotor, it is easy to see that the radiationsensitivity lobe will be stabilized in space for small angular motionsof the envelope. Consequently, if the device is included in a targetseeker for projectiles the radiation sensitivity lobe of the targetseeker will remain fixed in space in spite of the fact that theprojectile tumbles. It is thus achieved, by the simple measure ofselecting the refractive index for the diffraction prism, of which thegyro rotor is a part, that the radiation lobe will change its angle asmuch as the spin axis for small motions of the envelope.

It may sometimes be difficult to achieve a 1:1 ratio between an angularchange of the spin axis of the gyro rotor and the resulting angularchange of the radiation sensitivity lobe for outgoing or incomingradiation. The said 1:1 ratio can then be achieved by combining thedeflection device with a lens system having a suitable diffraction.

Preferably the radiation or sensitivity lobe is always in parallel withthe spin axis.

A deflection device in the form of an adjustable optical prism and usedas scanner in a target seeker for projectiles is shown in U.S. Pat. No.4,436,260. However, in this patent the deflection body is not impartedwith spin rotation and it only serves to deflect a radiation beam. Suchdevice cannot be used for stabilizing the direction of a radiation lobein space.

The deflection device according to the invention, operating bytransmission of radiation, has many advantages as compared with adeflection device operating by reflection. The radiation path can bemade symmetrical, which may be difficult or impossible to achieve in areflecting device. In certain applications such symmetry is essential.Secondly, since a transmissive deflection device and thetransmitter/receiver can be placed in line one after the other, themechanical construction will be very simple and of minimal volume.

The space stabilizing effect necessitates that no precession torques betransferred to the rotor. This can be achieved under continuous drivingof the rotor by using a spin drive, which does not produce any suchtorques. In a simplier embodiment, involving smaller demands on thequality of the spin drive, this drive of the rotor can bedisconnectable.

Besides the described space stabilization of the radiation orsensitivity lobe, in many applications such lobe must also be controlledto assume any desired direction relative to its own space reference. Forthis purpose a preferred embodiment of the device according to theinvention is furthermore provided with torque generators, which are ableto transfer turning torques to the deflection body about two mutuallyperpendicular axes relative to the spin axis.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is illustrated by means of example with reference to theaccompanying drawings, in which

FIG. 1 shows a longitudinal sectional view of a projectile with agyrostabilized deflection device according to the invention and

FIG. 2 shows a sectional view through the deflection device, taken alongthe line A--A in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In FIG. 1 reference numeral 10 designates a projectile envelope, while11 is a gyrostabilized deflection device according to the invention,fixedly mounted in the envelope. A converging lens is also mounted inthe envelope, and also a transmitter/receiver 13. The central axis C ofthe projectile forms at the same time the central axis for thedeflection device and lens. The deflection device can form agyrostabilized platform in a target seeker, which for example operateswith electromagnetic energy in the millimeter wavelength range.

The deflection device consists of a support 14 fixedly mounted in theenvelope 10 and having a spherical recess 15, in which a movabledeflection body 16 with spherical outer contour 17, or ball, isintroduced. The fixed support 14 is in the shown example composed bythree parts: an outer circular cylindrical ring 18 of soft magneticmaterial, an intermediate prism 19 of non-magnetic material and acentral part 20 of a material having a suitable refractive index for thetransmitted radiation. The parts 19 and 20 are the elements which withthe said recess 15 form together a housing or seat for the movable ball16. The ball 16 is in the shown example composed by two parts: an outerring-shaped part 21 with a central recess 22 and a hemispherical prismpart 23. In operation the incoming and outgoing radiation passes throughthe recess 22 in the ball 16 and through the prisms 23 and 20, which incombination form a diffraction prism or "optical wedge" which forms aradiation lobe for the transmitted or received radiation, andfurthermore through the lens 12. The central ray for such a radiationlobe is shown in the drawing and designated with L. As a result of itsspherical shape the ball 16 is free to move by a turning or rotationalmotion in all three rotational degrees of freedom in its recess 15. Theball 16 is shaped so its center of gravity coincides with the rotationalcenter for the said motions, whereby no torques will be transferred tothe ball during acceleration and deceleration of the envelope 10 inwhich the device 11 is mounted.

In order to be able to transfer torques to the ball 16 for turning thesame about two axes 01 and 02, a magnetic torque generator is used ofthe kind described and shown in Swedish Pat. No. SE 8502509-6. Forturning the ball 16 in one direction about the axis 01 there are twomagnetic poles 24 and 25 with electrical windings 26, 27. For turningthe ball in the opposite direction about the same axis 01 there are twomagnetic poles 28, 29 with electrical windings 30, 31. For turning theball 16 about the axis 02 there are similar magnetic pole pairs, asshown in FIG. 2 by the magnetic poles 32, 33 and associated windings.The fixed magnetic poles cooperate with a soft magnetic part 34 of themovable ball 16, which part 34 terminates in an equatorial ring 35 ofsoft magnetic material on the surface of the ball, which ball for therest is made of non-magnetic material. The outer circular cylindricalfixed ring 18 of soft magnetic material interconnects the outwardlyfacing ends of all magnetic poles with each other and will close allmagnetic field paths.

In order to be able to sense the instantaneous angular position of theball the fixed part of the deflection device comprises an angle detector36, which for example cooperates with an optical marking on the surfaceof the movable ball 16.

Between the spherical recess 15 in the fixed support 14 and the outerspherical surface 17 of the ball 16 there is an air-gap 37 which isactive as bearing for the ball. The air-gap is maintained by continuoussupply of compressed air to nozzles, which terminate in the said gap. InFIG. 2 four such nozzles with supply channels are shown and designatedwith 38, 39, 40, 41.

Furthermore the ball 16 is driven so as to make a rapid spin rotationabout a spin axis 03. The spin rotation can be produced by means of anelectrical spin motor or by air driving. In the shown example the ball16 is rotated about the spin axis 03 by means of oblique jets of air,produced by nozzles 42, 43 with supply channels and acting on the flatoutside of the ball. Hereby no precession torques will be transferred tothe ball.

By its rotation about the spin axis 03 the ball 16 will form a gyrorotor, which as a result of its rotatability about the axes 01 and 02 issupported in a similar manner as in a two-axes gimbal support. Thecentral hemispherical prism part 23 of this gyro rotor forms at the sametime in combination with the central prism 20 of the fixed support 14 avariable diffraction prism for the transmitted radiation, having a planesurface 44 which serves as an input/output surface for the radiation.Surface 44 forms a variable angle with a plane surface 45 of the prismpart of support 14, which said last surface also serves as output/inputsurface for the radiation. Within the envelope 10 thetransmitter/receiver 13 for the transmitted radiation is arranged on thecentral axis of the deflection device. By setting the movable prismsurface 44 of the rotor 16 at different angles relative to the prismsurface 45 of the fixed support 14, the direction for the outgoingand/or incoming radiation, in the drawing represented by the central rayL' of the radiation lobe, can be set arbitrarily. Decisive for how thedirection of the radiation or sensitivity lobe varies with a variationof the angular setting of the rotor 16 about the axes 01 and 02 is therefractive index for the materials of which the prisms 23 and 20included in the composite diffraction prism are made, in combinationwith the diffraction produced by the lens 12. According to the inventionthe refractive index for the prisms 23 and 20, which suitably are madeof the same material, is selected in such manner that the outgoingradiation or sensitivity lobe represented by L' is always parallel withthe spin axis 03 of the rotor. In the drawing the lobe center line L'and the spin axis 03 both form an angle α with the projectile symmetrycenter line C. As the gyro rotor 16 in absence of precession torquestransmitted to the same tends to maintain a set position in space, thiswill mean that the radiation lobe will be space stabilized for smallangular motions of the envelope 10. From this space reference the lobecan then be controlled in any desired manner by transferring torques tothe gyro rotor via the two-axis electromagnetic torque generator.

The refractive index of the material of which the prisms 23 and 20included in the diffraction prism are made can be selected so that thediffraction prism alone gives rise to the desired 1:1 ratio between anangular change of direction of the radiation or sensitivity lobe and anangular change of direction. The spin axis of the rotor, the lens 12will then be superfluous and can be omitted. If a lens 12 is required itmay, instead of being made as a separate lens, be integrated with thedeflection device by giving the prism surface 44 or the surface 45, orboth, a concave or convex shape.

Examples of suitable materials for prisms 20 and 23 for different kindsof radiation are as follows:

radar radiation: plastics and ceramics,

IR-radiation: crystalline materials, as silicon, germanium, zinkselenideand others; also certain glasses and plastics,

visible light: glass and plastics,

ultrasonic radiation: plastics and metals.

If the device has for its only purpose to stabilize the direction of aradiation lobe in space the torque generator will be superfluous and canbe omitted. The spin motor, which also can be of electrical type, may beso constructed that it drives the gyro rotor to a home position and canfurthermore be disconnectable, so that the rotor after disconnectionrotates freely.

We claim:
 1. A gyro stabilized optical radiation deflection device formounting in an envelope which includes a transmitter and/or receiver ofradiation outgoing from or incoming to such envelope, said device beingin the radiation path from/to such transmitter or receiver and providinga directed sensitivity lobe for said radiation, said envelope beingsubject to motions relative to fixed spatial reference directions; saiddeflection device comprising: a rotatable deflection body having aspherical outer contour and which is seated in a spherical recess in asupport which is fixedly connected to said envelope, so that said bodyis movable in three rotational degrees of freedom in said recess; andmeans for imparting rapid rotation to said body about a spin axis whichsubstantially coincides with the direction of said radiation sensitivitylobe, so that said body serves as a gyro rotor; characterized in that:acentral portion of said rotor and a central portion of said recess areprisms transparent to said radiation, and together form an adjustablediffraction prism for deflecting said radiation sensitivity lobe; saidprism portions of said recess and said gyro motor each have a wallserving as an input/output surface for said radiation; and said prismportions of said recess and said gyro rotor are of materials havingrefractive indices such that an angular change in the direction of saidenvelope relative to the spin axis of said gyro rotor causes saiddiffraction prism to produce a corresponding angular change in directionof outgoing and/or incoming radiation thereto, whereby a correspondingangular change in direction of said radiation sensitivity lobe isproduced relative to said envelope.
 2. A gyro stabilized opticalradiation deflection device as claimed in claim 1, further comprising alens providing a further diffraction which together with the diffractionprovided by said diffraction prism results in a 1:1 ratio between anangular change in direction of the spin axis of said gyro rotor and theresulting angular change in direction of said radiation sensitivitylobe.
 3. A gyro stabilized optical radiation deflection device asclaimed in claim 1 or 2, wherein said radiation sensitivity lobe ismaintained parallel to the spin axis of said gyro rotor.
 4. A gyrostabilized optical radiation deflection device as claimed in claim 1 or2, comprising a torque generator for applying turning torques to saidgyro rotor about two axes which are mutually substantially perpendicularrelative to said spin axis.
 5. A gyro stabilized optical radiationdeflection device as claimed in claim 1, 2 or 4, wherein said gyro rotorcomprises an outer ring shaped part having a central opening throughwhich radiation may pass to said central prism portion of said gyrorotor.